We’re kicking off the new year with a classic shark – the Great Hammerhead. Known for their distinct silhouette, the Great Hammerhead is the largest species of hammerhead on the planet.    

With a distinct notch on the centre of their head, the Great Hammerhead is light grey or brown above and white below. Reaching a maximum size of around six metres, this is a big shark. There are nine species of hammerhead. Identifying them often relies on looking at head shape. The Great Hammerhead has a much straighter front edge compared to the Scalloped and Smooth Hammerheads. 

The unique hammer-shaped head (a.k.a. cephlafoil) improves their manoeuvrability. As the position of their eyes enable them to see 360°. And enhances their ability to detect electrical currents, a sixth sense that all sharks have. Sharks have lots of tiny pores covering their head and snout, called ampullae of Lorenzini. These are extremely sensitive and can detect even the faintest of electrical fields. Including those generated by the Earth’s geomagnetic field, or muscle contractions in prey. The broad flat head of a hammerhead provides a much larger surface area for these pores. Which is why they’re so good at finding prey - such as stingrays - completely buried beneath the sand. 

Great Hammerheads are nomadic and seasonally migratory. They move towards the equator during the winter and then towards the poles during the summer. Unlike other species, they are solitary and migrate up to 1,200km (750 miles) alone.

The Great Hammerhead is Critically Endangered. Populations have declined in recent years. They are targeted and also caught as bycatch.

Although large and powerful, research has shown that Great Hammerheads are quite fragile. They are particularly vulnerable to the stress of capture. Recent research has found that individuals that are hooked have a 50% chance of dying following release. Combating the declining populations comes down to, as always, implementing scientifically informed catch limits and enforcing these. 

The species is important for dive tourism in some areas. In the video below, head of marketing for the Shark Trust - Caroline, takes in the view as a Great Hammerheads cruise by. They are a true sight to behold.

SCIENTIFIC NAME:  Sphyrna mokarran

FAMILY:  Sphyrnidae

MAXIMUM SIZE:  610cm 

DIET:  Varied. Preference for stingrays, other rays and marine catfish.

DISTRIBUTION: Worldwide, tropical seas. 

HABITAT:  Coastal-pelagic and semi-oceanic. Close inshore to well offshore. 1-300m or more.

CONSERVATION STATUS

Images from Frogfish Photography 

Distribution Map from Wikimedia Commons